/*
** This file is in the public domain, so clarified as of
** 1996-06-05 by Arthur David Olson.
*/

/*
** Leap second handling from Bradley White.
** POSIX-style TZ environment variable handling from Guy Harris.
*/

/*LINTLIBRARY*/

#include "private.h"
#include "tzfile.h"
#include "fcntl.h"

#ifndef TZ_ABBR_MAX_LEN
#define TZ_ABBR_MAX_LEN 16
#endif /* !defined TZ_ABBR_MAX_LEN */

#ifndef TZ_ABBR_CHAR_SET
#define TZ_ABBR_CHAR_SET \
  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 :+-._"
#endif /* !defined TZ_ABBR_CHAR_SET */

#ifndef TZ_ABBR_ERR_CHAR
#define TZ_ABBR_ERR_CHAR  '_'
#endif /* !defined TZ_ABBR_ERR_CHAR */

/*
** SunOS 4.1.1 headers lack O_BINARY.
*/

#ifdef O_BINARY
#define OPEN_MODE (O_RDONLY | O_BINARY)
#endif /* defined O_BINARY */
#ifndef O_BINARY
#define OPEN_MODE O_RDONLY
#endif /* !defined O_BINARY */

#ifndef WILDABBR
/*
** Someone might make incorrect use of a time zone abbreviation:
**  1.  They might reference tzname[0] before calling tzset (explicitly
**    or implicitly).
**  2.  They might reference tzname[1] before calling tzset (explicitly
**    or implicitly).
**  3.  They might reference tzname[1] after setting to a time zone
**    in which Daylight Saving Time is never observed.
**  4.  They might reference tzname[0] after setting to a time zone
**    in which Standard Time is never observed.
**  5.  They might reference tm.TM_ZONE after calling offtime.
** What's best to do in the above cases is open to debate;
** for now, we just set things up so that in any of the five cases
** WILDABBR is used. Another possibility: initialize tzname[0] to the
** string "tzname[0] used before set", and similarly for the other cases.
** And another: initialize tzname[0] to "ERA", with an explanation in the
** manual page of what this "time zone abbreviation" means (doing this so
** that tzname[0] has the "normal" length of three characters).
*/
#define WILDABBR  "   "
#endif /* !defined WILDABBR */

static char   wildabbr[] = WILDABBR;

static const char gmt[] = "GMT";

/*
** The DST rules to use if TZ has no rules and we can't load TZDEFRULES.
** We default to US rules as of 1999-08-17.
** POSIX 1003.1 section 8.1.1 says that the default DST rules are
** implementation dependent; for historical reasons, US rules are a
** common default.
*/
#ifndef TZDEFRULESTRING
#define TZDEFRULESTRING ",M4.1.0,M10.5.0"
#endif /* !defined TZDEFDST */

struct ttinfo         /* time type information */
{
  int_fast32_t  tt_gmtoff;  /* UT offset in seconds */
  int   tt_isdst; /* used to set tm_isdst */
  int   tt_abbrind; /* abbreviation list index */
  int   tt_ttisstd; /* TRUE if transition is std time */
  int   tt_ttisgmt; /* TRUE if transition is UT */
};

struct lsinfo         /* leap second information */
{
  time_t    ls_trans; /* transition time */
  int_fast64_t  ls_corr;  /* correction to apply */
};

#define BIGGEST(a, b) (((a) > (b)) ? (a) : (b))

#ifdef TZNAME_MAX
#define MY_TZNAME_MAX TZNAME_MAX
#endif /* defined TZNAME_MAX */
#ifndef TZNAME_MAX
#define MY_TZNAME_MAX 255
#endif /* !defined TZNAME_MAX */

struct state
{
  int   leapcnt;
  int   timecnt;
  int   typecnt;
  int   charcnt;
  int   goback;
  int   goahead;
  time_t    ats[TZ_MAX_TIMES];
  unsigned char types[TZ_MAX_TIMES];
  struct ttinfo ttis[TZ_MAX_TYPES];
  char    chars[BIGGEST(BIGGEST(TZ_MAX_CHARS + 1, sizeof gmt),
                        (2 * (MY_TZNAME_MAX + 1)))];
  struct lsinfo lsis[TZ_MAX_LEAPS];
  int   defaulttype; /* for early times or if no transitions */
};

struct rule
{
  int   r_type;   /* type of rule--see below */
  int   r_day;    /* day number of rule */
  int   r_week;   /* week number of rule */
  int   r_mon;    /* month number of rule */
  int_fast32_t  r_time;   /* transition time of rule */
};

#define JULIAN_DAY    0 /* Jn - Julian day */
#define DAY_OF_YEAR   1 /* n - day of year */
#define MONTH_NTH_DAY_OF_WEEK 2 /* Mm.n.d - month, week, day of week */

/*
** Prototypes for static functions.
*/

static int_fast32_t detzcode(const char *codep);
static time_t   detzcode64(const char *codep);
static int    differ_by_repeat(time_t t1, time_t t0);
static const char  *getzname(const char *strp) ATTRIBUTE_PURE;
static const char  *getqzname(const char *strp, const int delim)
ATTRIBUTE_PURE;
static const char  *getnum(const char *strp, int *nump, int min,
                           int max);
static const char  *getsecs(const char *strp, int_fast32_t *secsp);
static const char  *getoffset(const char *strp, int_fast32_t *offsetp);
static const char  *getrule(const char *strp, struct rule *rulep);
static void   gmtload(struct state *sp);
static struct tm   *gmtsub(const time_t *timep, int_fast32_t offset,
                           struct tm *tmp);
static struct tm   *localsub(const time_t *timep, int_fast32_t offset,
                             struct tm *tmp);
static int    increment_overflow(int *number, int delta);
static int    leaps_thru_end_of(int y) ATTRIBUTE_PURE;
static int    increment_overflow32(int_fast32_t *number, int delta);
static int    normalize_overflow32(int_fast32_t *tensptr,
                                   int *unitsptr, int base);
static int    normalize_overflow(int *tensptr, int *unitsptr,
                                 int base);
static void   settzname(void);
static time_t   time1(struct tm *tmp,
                      struct tm * (*funcp)(const time_t *,
                                           int_fast32_t, struct tm *),
                      int_fast32_t offset);
static time_t   time2(struct tm *tmp,
                      struct tm * (*funcp)(const time_t *,
                                           int_fast32_t, struct tm *),
                      int_fast32_t offset, int *okayp);
static time_t   time2sub(struct tm *tmp,
                         struct tm * (*funcp)(const time_t *,
                                              int_fast32_t, struct tm *),
                         int_fast32_t offset, int *okayp, int do_norm_secs);
static struct tm   *timesub(const time_t *timep, int_fast32_t offset,
                            const struct state *sp, struct tm *tmp);
static int    tmcomp(const struct tm *atmp,
                     const struct tm *btmp);
static time_t   transtime(time_t janfirst, int year,
                          const struct rule *rulep, int_fast32_t offset)
ATTRIBUTE_PURE;
static int    typesequiv(const struct state *sp, int a, int b);
static int    tzload(const char *name, struct state *sp,
                     int doextend);
static int    tzparse(const char *name, struct state *sp,
                      int lastditch);

#ifdef ALL_STATE
static struct state  *lclptr;
static struct state  *gmtptr;
#endif /* defined ALL_STATE */

#ifndef ALL_STATE
static struct state lclmem;
static struct state gmtmem;
#define lclptr    (&lclmem)
#define gmtptr    (&gmtmem)
#endif /* State Farm */

#ifndef TZ_STRLEN_MAX
#define TZ_STRLEN_MAX 255
#endif /* !defined TZ_STRLEN_MAX */

static char   lcl_TZname[TZ_STRLEN_MAX + 1];
static int    lcl_is_set;
static int    gmt_is_set;

char       *tzname[2] =
{
  wildabbr,
  wildabbr
};

/*
** Section 4.12.3 of X3.159-1989 requires that
**  Except for the strftime function, these functions [asctime,
**  ctime, gmtime, localtime] return values in one of two static
**  objects: a broken-down time structure and an array of char.
** Thanks to Paul Eggert for noting this.
*/

static struct tm  tm;

#ifdef USG_COMPAT
long      timezone = 0;
int     daylight = 0;
#endif /* defined USG_COMPAT */

#ifdef ALTZONE
long      altzone = 0;
#endif /* defined ALTZONE */

static int_fast32_t
detzcode(const char *const codep)
{
  register int_fast32_t result;
  register int    i;

  result = (codep[0] & 0x80) ? -1 : 0;
  for (i = 0; i < 4; ++i) {
    result = (result << 8) | (codep[i] & 0xff);
  }
  return result;
}

static time_t
detzcode64(const char *const codep)
{
  register time_t result;
  register int  i;

  result = (codep[0] & 0x80) ? (~(int_fast64_t) 0) : 0;
  for (i = 0; i < 8; ++i) {
    result = result * 256 + (codep[i] & 0xff);
  }
  return result;
}

static void
settzname(void)
{
  register struct state *const sp = lclptr;
  register int      i;

  tzname[0] = wildabbr;
  tzname[1] = wildabbr;
#ifdef USG_COMPAT
  daylight = 0;
  timezone = 0;
#endif /* defined USG_COMPAT */
#ifdef ALTZONE
  altzone = 0;
#endif /* defined ALTZONE */
#ifdef ALL_STATE
  if (sp == NULL) {
    tzname[0] = tzname[1] = gmt;
    return;
  }
#endif /* defined ALL_STATE */
  /*
  ** And to get the latest zone names into tzname. . .
  */
  for (i = 0; i < sp->typecnt; ++i) {
    register const struct ttinfo *const  ttisp = &sp->ttis[i];

    tzname[ttisp->tt_isdst] = &sp->chars[ttisp->tt_abbrind];
  }
  for (i = 0; i < sp->timecnt; ++i) {
    register const struct ttinfo *const  ttisp =
              &sp->ttis[
                  sp->types[i]];

    tzname[ttisp->tt_isdst] =
        &sp->chars[ttisp->tt_abbrind];
#ifdef USG_COMPAT
    if (ttisp->tt_isdst) {
      daylight = 1;
    }
    if (!ttisp->tt_isdst) {
      timezone = -(ttisp->tt_gmtoff);
    }
#endif /* defined USG_COMPAT */
#ifdef ALTZONE
    if (ttisp->tt_isdst) {
      altzone = -(ttisp->tt_gmtoff);
    }
#endif /* defined ALTZONE */
  }
  /*
  ** Finally, scrub the abbreviations.
  ** First, replace bogus characters.
  */
  for (i = 0; i < sp->charcnt; ++i)
    if (strchr(TZ_ABBR_CHAR_SET, sp->chars[i]) == NULL) {
      sp->chars[i] = TZ_ABBR_ERR_CHAR;
    }
  /*
  ** Second, truncate long abbreviations.
  */
  for (i = 0; i < sp->typecnt; ++i) {
    register const struct ttinfo *const  ttisp = &sp->ttis[i];
    register char        *cp = &sp->chars[ttisp->tt_abbrind];

    if (strlen(cp) > TZ_ABBR_MAX_LEN &&
        strcmp(cp, GRANDPARENTED) != 0) {
      *(cp + TZ_ABBR_MAX_LEN) = '\0';
    }
  }
}

static int
differ_by_repeat(const time_t t1, const time_t t0)
{
  if (TYPE_BIT(time_t) - TYPE_SIGNED(time_t) < SECSPERREPEAT_BITS) {
    return 0;
  }
  return t1 - t0 == SECSPERREPEAT;
}

static int
tzload(register const char *name, register struct state *const sp,
       register const int doextend)
{
  register const char    *p;
  register int      i;
  register int      fid;
  register int      stored;
  register int      nread;
  typedef union
  {
    struct tzhead tzhead;
    char    buf[2 * sizeof(struct tzhead) +
                2 * sizeof * sp +
                4 * TZ_MAX_TIMES];
  } u_t;
#ifdef ALL_STATE
  register u_t       *up;

  up = (u_t *) calloc(1, sizeof * up);
  if (up == NULL) {
    return -1;
  }
#else /* !defined ALL_STATE */
  u_t       u;
  register u_t *const    up = &u;
#endif /* !defined ALL_STATE */

  sp->goback = sp->goahead = FALSE;
  if (name == NULL && (name = TZDEFAULT) == NULL) {
    goto oops;
  }
  {
    register int  doaccess;
    /*
    ** Section 4.9.1 of the C standard says that
    ** "FILENAME_MAX expands to an integral constant expression
    ** that is the size needed for an array of char large enough
    ** to hold the longest file name string that the implementation
    ** guarantees can be opened."
    */
    char    fullname[FILENAME_MAX + 1];

    if (name[0] == ':') {
      ++name;
    }
    doaccess = name[0] == '/';
    if (!doaccess) {
      if ((p = TZDIR) == NULL) {
        goto oops;
      }
      if ((strlen(p) + strlen(name) + 1) >= sizeof fullname) {
        goto oops;
      }
      (void) strcpy(fullname, p);
      (void) strcat(fullname, "/");
      (void) strcat(fullname, name);
      /*
      ** Set doaccess if '.' (as in "../") shows up in name.
      */
      if (strchr(name, '.') != NULL) {
        doaccess = TRUE;
      }
      name = fullname;
    }
    if (doaccess && access(name, R_OK) != 0) {
      goto oops;
    }
    if ((fid = open(name, OPEN_MODE)) == -1) {
      goto oops;
    }
  }
  nread = read(fid, up->buf, sizeof up->buf);
  if (close(fid) < 0 || nread <= 0) {
    goto oops;
  }
  for (stored = 4; stored <= 8; stored *= 2) {
    int   ttisstdcnt;
    int   ttisgmtcnt;

    ttisstdcnt = (int) detzcode(up->tzhead.tzh_ttisstdcnt);
    ttisgmtcnt = (int) detzcode(up->tzhead.tzh_ttisgmtcnt);
    sp->leapcnt = (int) detzcode(up->tzhead.tzh_leapcnt);
    sp->timecnt = (int) detzcode(up->tzhead.tzh_timecnt);
    sp->typecnt = (int) detzcode(up->tzhead.tzh_typecnt);
    sp->charcnt = (int) detzcode(up->tzhead.tzh_charcnt);
    p = up->tzhead.tzh_charcnt + sizeof up->tzhead.tzh_charcnt;
    if (sp->leapcnt < 0 || sp->leapcnt > TZ_MAX_LEAPS ||
        sp->typecnt <= 0 || sp->typecnt > TZ_MAX_TYPES ||
        sp->timecnt < 0 || sp->timecnt > TZ_MAX_TIMES ||
        sp->charcnt < 0 || sp->charcnt > TZ_MAX_CHARS ||
        (ttisstdcnt != sp->typecnt && ttisstdcnt != 0) ||
        (ttisgmtcnt != sp->typecnt && ttisgmtcnt != 0)) {
      goto oops;
    }
    if (nread - (p - up->buf) <
        sp->timecnt * stored +    /* ats */
        sp->timecnt +     /* types */
        sp->typecnt * 6 +   /* ttinfos */
        sp->charcnt +     /* chars */
        sp->leapcnt * (stored + 4) +  /* lsinfos */
        ttisstdcnt +      /* ttisstds */
        ttisgmtcnt) {   /* ttisgmts */
      goto oops;
    }
    for (i = 0; i < sp->timecnt; ++i) {
      sp->ats[i] = (stored == 4) ?
                   detzcode(p) : detzcode64(p);
      p += stored;
    }
    for (i = 0; i < sp->timecnt; ++i) {
      sp->types[i] = (unsigned char) * p++;
      if (sp->types[i] >= sp->typecnt) {
        goto oops;
      }
    }
    for (i = 0; i < sp->typecnt; ++i) {
      register struct ttinfo   *ttisp;

      ttisp = &sp->ttis[i];
      ttisp->tt_gmtoff = detzcode(p);
      p += 4;
      ttisp->tt_isdst = (unsigned char) * p++;
      if (ttisp->tt_isdst != 0 && ttisp->tt_isdst != 1) {
        goto oops;
      }
      ttisp->tt_abbrind = (unsigned char) * p++;
      if (ttisp->tt_abbrind < 0 ||
          ttisp->tt_abbrind > sp->charcnt) {
        goto oops;
      }
    }
    for (i = 0; i < sp->charcnt; ++i) {
      sp->chars[i] = *p++;
    }
    sp->chars[i] = '\0';  /* ensure '\0' at end */
    for (i = 0; i < sp->leapcnt; ++i) {
      register struct lsinfo   *lsisp;

      lsisp = &sp->lsis[i];
      lsisp->ls_trans = (stored == 4) ?
                        detzcode(p) : detzcode64(p);
      p += stored;
      lsisp->ls_corr = detzcode(p);
      p += 4;
    }
    for (i = 0; i < sp->typecnt; ++i) {
      register struct ttinfo   *ttisp;

      ttisp = &sp->ttis[i];
      if (ttisstdcnt == 0) {
        ttisp->tt_ttisstd = FALSE;
      } else {
        ttisp->tt_ttisstd = *p++;
        if (ttisp->tt_ttisstd != TRUE &&
            ttisp->tt_ttisstd != FALSE) {
          goto oops;
        }
      }
    }
    for (i = 0; i < sp->typecnt; ++i) {
      register struct ttinfo   *ttisp;

      ttisp = &sp->ttis[i];
      if (ttisgmtcnt == 0) {
        ttisp->tt_ttisgmt = FALSE;
      } else {
        ttisp->tt_ttisgmt = *p++;
        if (ttisp->tt_ttisgmt != TRUE &&
            ttisp->tt_ttisgmt != FALSE) {
          goto oops;
        }
      }
    }
    /*
    ** Out-of-sort ats should mean we're running on a
    ** signed time_t system but using a data file with
    ** unsigned values (or vice versa).
    */
    for (i = 0; i < sp->timecnt; ++i)
      if ((i < sp->timecnt - 1 &&
           sp->ats[i] > sp->ats[i + 1]) ||
          (i == sp->timecnt - 1 && !TYPE_SIGNED(time_t) &&
           sp->ats[i] >
           ((stored == 4) ? INT32_MAX : INT64_MAX))) {
        if (TYPE_SIGNED(time_t)) {
          /*
          ** Ignore the end (easy).
          */
          sp->timecnt = i + 1;
        } else {
          /*
          ** Ignore the beginning (harder).
          */
          register int  j;

          /*
          ** Keep the record right before the
          ** epoch boundary,
          ** but tweak it so that it starts
          ** right with the epoch
          ** (thanks to Doug Bailey).
          */
          sp->ats[i] = 0;
          for (j = 0; j + i < sp->timecnt; ++j) {
            sp->ats[j] = sp->ats[j + i];
            sp->types[j] = sp->types[j + i];
          }
          sp->timecnt = j;
        }
        break;
      }
    /*
    ** If this is an old file, we're done.
    */
    if (up->tzhead.tzh_version[0] == '\0') {
      break;
    }
    nread -= p - up->buf;
    for (i = 0; i < nread; ++i) {
      up->buf[i] = p[i];
    }
    /*
    ** If this is a narrow time_t system, we're done.
    */
    if (stored >= (int) sizeof(time_t)) {
      break;
    }
  }
  if (doextend && nread > 2 &&
      up->buf[0] == '\n' && up->buf[nread - 1] == '\n' &&
      sp->typecnt + 2 <= TZ_MAX_TYPES) {
    struct state  ts;
    register int  result;

    up->buf[nread - 1] = '\0';
    result = tzparse(&up->buf[1], &ts, FALSE);
    if (result == 0 && ts.typecnt == 2 &&
        sp->charcnt + ts.charcnt <= TZ_MAX_CHARS) {
      for (i = 0; i < 2; ++i)
        ts.ttis[i].tt_abbrind +=
            sp->charcnt;
      for (i = 0; i < ts.charcnt; ++i)
        sp->chars[sp->charcnt++] =
            ts.chars[i];
      i = 0;
      while (i < ts.timecnt &&
             ts.ats[i] <=
             sp->ats[sp->timecnt - 1]) {
        ++i;
      }
      while (i < ts.timecnt &&
             sp->timecnt < TZ_MAX_TIMES) {
        sp->ats[sp->timecnt] =
            ts.ats[i];
        sp->types[sp->timecnt] =
            sp->typecnt +
            ts.types[i];
        ++sp->timecnt;
        ++i;
      }
      sp->ttis[sp->typecnt++] = ts.ttis[0];
      sp->ttis[sp->typecnt++] = ts.ttis[1];
    }
  }
  if (sp->timecnt > 1) {
    for (i = 1; i < sp->timecnt; ++i)
      if (typesequiv(sp, sp->types[i], sp->types[0]) &&
          differ_by_repeat(sp->ats[i], sp->ats[0])) {
        sp->goback = TRUE;
        break;
      }
    for (i = sp->timecnt - 2; i >= 0; --i)
      if (typesequiv(sp, sp->types[sp->timecnt - 1],
                     sp->types[i]) &&
          differ_by_repeat(sp->ats[sp->timecnt - 1],
                           sp->ats[i])) {
        sp->goahead = TRUE;
        break;
      }
  }
  /*
  ** If type 0 is is unused in transitions,
  ** it's the type to use for early times.
  */
  for (i = 0; i < sp->typecnt; ++i)
    if (sp->types[i] == 0) {
      break;
    }
  i = (i >= sp->typecnt) ? 0 : -1;
  /*
  ** Absent the above,
  ** if there are transition times
  ** and the first transition is to a daylight time
  ** find the standard type less than and closest to
  ** the type of the first transition.
  */
  if (i < 0 && sp->timecnt > 0 && sp->ttis[sp->types[0]].tt_isdst) {
    i = sp->types[0];
    while (--i >= 0)
      if (!sp->ttis[i].tt_isdst) {
        break;
      }
  }
  /*
  ** If no result yet, find the first standard type.
  ** If there is none, punt to type zero.
  */
  if (i < 0) {
    i = 0;
    while (sp->ttis[i].tt_isdst)
      if (++i >= sp->typecnt) {
        i = 0;
        break;
      }
  }
  sp->defaulttype = i;
#ifdef ALL_STATE
  free(up);
#endif /* defined ALL_STATE */
  return 0;
oops:
#ifdef ALL_STATE
  free(up);
#endif /* defined ALL_STATE */
  return -1;
}

static int
typesequiv(const struct state *const sp, const int a, const int b)
{
  register int  result;

  if (sp == NULL ||
      a < 0 || a >= sp->typecnt ||
      b < 0 || b >= sp->typecnt) {
    result = FALSE;
  } else {
    register const struct ttinfo   *ap = &sp->ttis[a];
    register const struct ttinfo   *bp = &sp->ttis[b];
    result = ap->tt_gmtoff == bp->tt_gmtoff &&
             ap->tt_isdst == bp->tt_isdst &&
             ap->tt_ttisstd == bp->tt_ttisstd &&
             ap->tt_ttisgmt == bp->tt_ttisgmt &&
             strcmp(&sp->chars[ap->tt_abbrind],
                    &sp->chars[bp->tt_abbrind]) == 0;
  }
  return result;
}

static const int  mon_lengths[2][MONSPERYEAR] =
{
  { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
  { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

static const int  year_lengths[2] =
{
  DAYSPERNYEAR, DAYSPERLYEAR
};

/*
** Given a pointer into a time zone string, scan until a character that is not
** a valid character in a zone name is found. Return a pointer to that
** character.
*/

static const char *
getzname(register const char *strp)
{
  register char c;

  while ((c = *strp) != '\0' && !is_digit(c) && c != ',' && c != '-' &&
         c != '+') {
    ++strp;
  }
  return strp;
}

/*
** Given a pointer into an extended time zone string, scan until the ending
** delimiter of the zone name is located. Return a pointer to the delimiter.
**
** As with getzname above, the legal character set is actually quite
** restricted, with other characters producing undefined results.
** We don't do any checking here; checking is done later in common-case code.
*/

static const char *
getqzname(register const char *strp, const int delim)
{
  register int  c;

  while ((c = *strp) != '\0' && c != delim) {
    ++strp;
  }
  return strp;
}

/*
** Given a pointer into a time zone string, extract a number from that string.
** Check that the number is within a specified range; if it is not, return
** NULL.
** Otherwise, return a pointer to the first character not part of the number.
*/

static const char *
getnum(register const char *strp, int *const nump, const int min, const int max)
{
  register char c;
  register int  num;

  if (strp == NULL || !is_digit(c = *strp)) {
    return NULL;
  }
  num = 0;
  do {
    num = num * 10 + (c - '0');
    if (num > max) {
      return NULL;  /* illegal value */
    }
    c = *++strp;
  } while (is_digit(c));
  if (num < min) {
    return NULL;  /* illegal value */
  }
  *nump = num;
  return strp;
}

/*
** Given a pointer into a time zone string, extract a number of seconds,
** in hh[:mm[:ss]] form, from the string.
** If any error occurs, return NULL.
** Otherwise, return a pointer to the first character not part of the number
** of seconds.
*/

static const char *
getsecs(register const char *strp, int_fast32_t *const secsp)
{
  int num;

  /*
  ** `HOURSPERDAY * DAYSPERWEEK - 1' allows quasi-Posix rules like
  ** "M10.4.6/26", which does not conform to Posix,
  ** but which specifies the equivalent of
  ** ``02:00 on the first Sunday on or after 23 Oct''.
  */
  strp = getnum(strp, &num, 0, HOURSPERDAY * DAYSPERWEEK - 1);
  if (strp == NULL) {
    return NULL;
  }
  *secsp = num * (int_fast32_t) SECSPERHOUR;
  if (*strp == ':') {
    ++strp;
    strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
    if (strp == NULL) {
      return NULL;
    }
    *secsp += num * SECSPERMIN;
    if (*strp == ':') {
      ++strp;
      /* `SECSPERMIN' allows for leap seconds. */
      strp = getnum(strp, &num, 0, SECSPERMIN);
      if (strp == NULL) {
        return NULL;
      }
      *secsp += num;
    }
  }
  return strp;
}

/*
** Given a pointer into a time zone string, extract an offset, in
** [+-]hh[:mm[:ss]] form, from the string.
** If any error occurs, return NULL.
** Otherwise, return a pointer to the first character not part of the time.
*/

static const char *
getoffset(register const char *strp, int_fast32_t *const offsetp)
{
  register int  neg = 0;

  if (*strp == '-') {
    neg = 1;
    ++strp;
  } else if (*strp == '+') {
    ++strp;
  }
  strp = getsecs(strp, offsetp);
  if (strp == NULL) {
    return NULL;  /* illegal time */
  }
  if (neg) {
    *offsetp = -*offsetp;
  }
  return strp;
}

/*
** Given a pointer into a time zone string, extract a rule in the form
** date[/time]. See POSIX section 8 for the format of "date" and "time".
** If a valid rule is not found, return NULL.
** Otherwise, return a pointer to the first character not part of the rule.
*/

static const char *
getrule(const char *strp, register struct rule *const rulep)
{
  if (*strp == 'J') {
    /*
    ** Julian day.
    */
    rulep->r_type = JULIAN_DAY;
    ++strp;
    strp = getnum(strp, &rulep->r_day, 1, DAYSPERNYEAR);
  } else if (*strp == 'M') {
    /*
    ** Month, week, day.
    */
    rulep->r_type = MONTH_NTH_DAY_OF_WEEK;
    ++strp;
    strp = getnum(strp, &rulep->r_mon, 1, MONSPERYEAR);
    if (strp == NULL) {
      return NULL;
    }
    if (*strp++ != '.') {
      return NULL;
    }
    strp = getnum(strp, &rulep->r_week, 1, 5);
    if (strp == NULL) {
      return NULL;
    }
    if (*strp++ != '.') {
      return NULL;
    }
    strp = getnum(strp, &rulep->r_day, 0, DAYSPERWEEK - 1);
  } else if (is_digit(*strp)) {
    /*
    ** Day of year.
    */
    rulep->r_type = DAY_OF_YEAR;
    strp = getnum(strp, &rulep->r_day, 0, DAYSPERLYEAR - 1);
  } else { return NULL; }   /* invalid format */
  if (strp == NULL) {
    return NULL;
  }
  if (*strp == '/') {
    /*
    ** Time specified.
    */
    ++strp;
    strp = getoffset(strp, &rulep->r_time);
  } else { rulep->r_time = 2 * SECSPERHOUR; } /* default = 2:00:00 */
  return strp;
}

/*
** Given the Epoch-relative time of January 1, 00:00:00 UTC, in a year, the
** year, a rule, and the offset from UT at the time that rule takes effect,
** calculate the Epoch-relative time that rule takes effect.
*/

static time_t
transtime(const time_t janfirst, const int year,
          register const struct rule *const rulep, const int_fast32_t offset)
{
  register int  leapyear;
  register time_t value;
  register int  i;
  int   d, m1, yy0, yy1, yy2, dow;

  INITIALIZE(value);
  leapyear = isleap(year);
  switch (rulep->r_type) {

    case JULIAN_DAY:
      /*
      ** Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
      ** years.
      ** In non-leap years, or if the day number is 59 or less, just
      ** add SECSPERDAY times the day number-1 to the time of
      ** January 1, midnight, to get the day.
      */
      value = janfirst + (rulep->r_day - 1) * SECSPERDAY;
      if (leapyear && rulep->r_day >= 60) {
        value += SECSPERDAY;
      }
      break;

    case DAY_OF_YEAR:
      /*
      ** n - day of year.
      ** Just add SECSPERDAY times the day number to the time of
      ** January 1, midnight, to get the day.
      */
      value = janfirst + rulep->r_day * SECSPERDAY;
      break;

    case MONTH_NTH_DAY_OF_WEEK:
      /*
      ** Mm.n.d - nth "dth day" of month m.
      */
      value = janfirst;
      for (i = 0; i < rulep->r_mon - 1; ++i) {
        value += mon_lengths[leapyear][i] * SECSPERDAY;
      }

      /*
      ** Use Zeller's Congruence to get day-of-week of first day of
      ** month.
      */
      m1 = (rulep->r_mon + 9) % 12 + 1;
      yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
      yy1 = yy0 / 100;
      yy2 = yy0 % 100;
      dow = ((26 * m1 - 2) / 10 +
             1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
      if (dow < 0) {
        dow += DAYSPERWEEK;
      }

      /*
      ** "dow" is the day-of-week of the first day of the month. Get
      ** the day-of-month (zero-origin) of the first "dow" day of the
      ** month.
      */
      d = rulep->r_day - dow;
      if (d < 0) {
        d += DAYSPERWEEK;
      }
      for (i = 1; i < rulep->r_week; ++i) {
        if (d + DAYSPERWEEK >=
            mon_lengths[leapyear][rulep->r_mon - 1]) {
          break;
        }
        d += DAYSPERWEEK;
      }

      /*
      ** "d" is the day-of-month (zero-origin) of the day we want.
      */
      value += d * SECSPERDAY;
      break;
  }

  /*
  ** "value" is the Epoch-relative time of 00:00:00 UT on the day in
  ** question. To get the Epoch-relative time of the specified local
  ** time on that day, add the transition time and the current offset
  ** from UT.
  */
  return value + rulep->r_time + offset;
}

/*
** Given a POSIX section 8-style TZ string, fill in the rule tables as
** appropriate.
*/

static int
tzparse(const char *name, register struct state *const sp,
        const int lastditch)
{
  const char       *stdname;
  const char       *dstname;
  size_t        stdlen;
  size_t        dstlen;
  int_fast32_t      stdoffset;
  int_fast32_t      dstoffset;
  register time_t    *atp;
  register unsigned char   *typep;
  register char      *cp;
  register int      load_result;
  static struct ttinfo    zttinfo;

  INITIALIZE(dstname);
  stdname = name;
  if (lastditch) {
    stdlen = strlen(name);  /* length of standard zone name */
    name += stdlen;
    if (stdlen >= sizeof sp->chars) {
      stdlen = (sizeof sp->chars) - 1;
    }
    stdoffset = 0;
  } else {
    if (*name == '<') {
      name++;
      stdname = name;
      name = getqzname(name, '>');
      if (*name != '>') {
        return (-1);
      }
      stdlen = name - stdname;
      name++;
    } else {
      name = getzname(name);
      stdlen = name - stdname;
    }
    if (*name == '\0') {
      return -1;
    }
    name = getoffset(name, &stdoffset);
    if (name == NULL) {
      return -1;
    }
  }
  load_result = tzload(TZDEFRULES, sp, FALSE);
  if (load_result != 0) {
    sp->leapcnt = 0;  /* so, we're off a little */
  }
  if (*name != '\0') {
    if (*name == '<') {
      dstname = ++name;
      name = getqzname(name, '>');
      if (*name != '>') {
        return -1;
      }
      dstlen = name - dstname;
      name++;
    } else {
      dstname = name;
      name = getzname(name);
      dstlen = name - dstname; /* length of DST zone name */
    }
    if (*name != '\0' && *name != ',' && *name != ';') {
      name = getoffset(name, &dstoffset);
      if (name == NULL) {
        return -1;
      }
    } else { dstoffset = stdoffset - SECSPERHOUR; }
    if (*name == '\0' && load_result != 0) {
      name = TZDEFRULESTRING;
    }
    if (*name == ',' || *name == ';') {
      struct rule start;
      struct rule end;
      register int  year;
      register int  yearlim;
      register time_t janfirst;
      time_t    starttime;
      time_t    endtime;

      ++name;
      if ((name = getrule(name, &start)) == NULL) {
        return -1;
      }
      if (*name++ != ',') {
        return -1;
      }
      if ((name = getrule(name, &end)) == NULL) {
        return -1;
      }
      if (*name != '\0') {
        return -1;
      }
      sp->typecnt = 2;  /* standard time and DST */
      /*
      ** Two transitions per year, from EPOCH_YEAR forward.
      */
      sp->ttis[0] = sp->ttis[1] = zttinfo;
      sp->ttis[0].tt_gmtoff = -dstoffset;
      sp->ttis[0].tt_isdst = 1;
      sp->ttis[0].tt_abbrind = stdlen + 1;
      sp->ttis[1].tt_gmtoff = -stdoffset;
      sp->ttis[1].tt_isdst = 0;
      sp->ttis[1].tt_abbrind = 0;
      atp = sp->ats;
      typep = sp->types;
      janfirst = 0;
      yearlim = EPOCH_YEAR + YEARSPERREPEAT;
      for (year = EPOCH_YEAR; year < yearlim; year++) {
        int_fast32_t yearsecs;

        starttime = transtime(janfirst, year, &start,
                              stdoffset);
        endtime = transtime(janfirst, year, &end,
                            dstoffset);
        yearsecs = (year_lengths[isleap(year)]
                    * SECSPERDAY);
        if (starttime > endtime
            || (starttime < endtime
                && (endtime - starttime
                    < (yearsecs
                       + (stdoffset - dstoffset))))) {
          if (&sp->ats[TZ_MAX_TIMES - 2] < atp) {
            break;
          }
          yearlim = year + YEARSPERREPEAT + 1;
          if (starttime > endtime) {
            *atp++ = endtime;
            *typep++ = 1; /* DST ends */
            *atp++ = starttime;
            *typep++ = 0; /* DST begins */
          } else {
            *atp++ = starttime;
            *typep++ = 0; /* DST begins */
            *atp++ = endtime;
            *typep++ = 1; /* DST ends */
          }
        }
        if (time_t_max - janfirst < yearsecs) {
          break;
        }
        janfirst += yearsecs;
      }
      sp->timecnt = atp - sp->ats;
      if (!sp->timecnt) {
        sp->typecnt = 1;  /* Perpetual DST.  */
      }
    } else {
      register int_fast32_t theirstdoffset;
      register int_fast32_t theirdstoffset;
      register int_fast32_t theiroffset;
      register int    isdst;
      register int    i;
      register int    j;

      if (*name != '\0') {
        return -1;
      }
      /*
      ** Initial values of theirstdoffset and theirdstoffset.
      */
      theirstdoffset = 0;
      for (i = 0; i < sp->timecnt; ++i) {
        j = sp->types[i];
        if (!sp->ttis[j].tt_isdst) {
          theirstdoffset =
              -sp->ttis[j].tt_gmtoff;
          break;
        }
      }
      theirdstoffset = 0;
      for (i = 0; i < sp->timecnt; ++i) {
        j = sp->types[i];
        if (sp->ttis[j].tt_isdst) {
          theirdstoffset =
              -sp->ttis[j].tt_gmtoff;
          break;
        }
      }
      /*
      ** Initially we're assumed to be in standard time.
      */
      isdst = FALSE;
      theiroffset = theirstdoffset;
      /*
      ** Now juggle transition times and types
      ** tracking offsets as you do.
      */
      for (i = 0; i < sp->timecnt; ++i) {
        j = sp->types[i];
        sp->types[i] = sp->ttis[j].tt_isdst;
        if (sp->ttis[j].tt_ttisgmt) {
          /* No adjustment to transition time */
        } else {
          /*
          ** If summer time is in effect, and the
          ** transition time was not specified as
          ** standard time, add the summer time
          ** offset to the transition time;
          ** otherwise, add the standard time
          ** offset to the transition time.
          */
          /*
          ** Transitions from DST to DDST
          ** will effectively disappear since
          ** POSIX provides for only one DST
          ** offset.
          */
          if (isdst && !sp->ttis[j].tt_ttisstd) {
            sp->ats[i] += dstoffset -
                          theirdstoffset;
          } else {
            sp->ats[i] += stdoffset -
                          theirstdoffset;
          }
        }
        theiroffset = -sp->ttis[j].tt_gmtoff;
        if (sp->ttis[j].tt_isdst) {
          theirdstoffset = theiroffset;
        } else { theirstdoffset = theiroffset; }
      }
      /*
      ** Finally, fill in ttis.
      */
      sp->ttis[0] = sp->ttis[1] = zttinfo;
      sp->ttis[0].tt_gmtoff = -stdoffset;
      sp->ttis[0].tt_isdst = FALSE;
      sp->ttis[0].tt_abbrind = 0;
      sp->ttis[1].tt_gmtoff = -dstoffset;
      sp->ttis[1].tt_isdst = TRUE;
      sp->ttis[1].tt_abbrind = stdlen + 1;
      sp->typecnt = 2;
    }
  } else {
    dstlen = 0;
    sp->typecnt = 1;    /* only standard time */
    sp->timecnt = 0;
    sp->ttis[0] = zttinfo;
    sp->ttis[0].tt_gmtoff = -stdoffset;
    sp->ttis[0].tt_isdst = 0;
    sp->ttis[0].tt_abbrind = 0;
  }
  sp->charcnt = stdlen + 1;
  if (dstlen != 0) {
    sp->charcnt += dstlen + 1;
  }
  if ((size_t) sp->charcnt > sizeof sp->chars) {
    return -1;
  }
  cp = sp->chars;
  (void) strncpy(cp, stdname, stdlen);
  cp += stdlen;
  *cp++ = '\0';
  if (dstlen != 0) {
    (void) strncpy(cp, dstname, dstlen);
    *(cp + dstlen) = '\0';
  }
  return 0;
}

static void
gmtload(struct state *const sp)
{
  if (tzload(gmt, sp, TRUE) != 0) {
    (void) tzparse(gmt, sp, TRUE);
  }
}

#ifndef STD_INSPIRED
/*
** A non-static declaration of tzsetwall in a system header file
** may cause a warning about this upcoming static declaration...
*/
static
#endif /* !defined STD_INSPIRED */
void
tzsetwall(void)
{
  if (lcl_is_set < 0) {
    return;
  }
  lcl_is_set = -1;

#ifdef ALL_STATE
  if (lclptr == NULL) {
    lclptr = calloc(1, sizeof * lclptr);
    if (lclptr == NULL) {
      settzname();  /* all we can do */
      return;
    }
  }
#endif /* defined ALL_STATE */
  if (tzload("/etc/localtime", lclptr, TRUE) != 0) {
    gmtload(lclptr);
  }
  settzname();
}

void
tzset(void)
{
  register const char  *name;

  name = getenv("TZ");
  if (name == NULL) {
    tzsetwall();
    return;
  }

  if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0) {
    return;
  }
  lcl_is_set = strlen(name) < sizeof lcl_TZname;
  if (lcl_is_set) {
    (void) strcpy(lcl_TZname, name);
  }

#ifdef ALL_STATE
  if (lclptr == NULL) {
    lclptr = calloc(1, sizeof * lclptr);
    if (lclptr == NULL) {
      settzname();  /* all we can do */
      return;
    }
  }
#endif /* defined ALL_STATE */
  if (*name == '\0') {
    /*
    ** User wants it fast rather than right.
    */
    lclptr->leapcnt = 0;    /* so, we're off a little */
    lclptr->timecnt = 0;
    lclptr->typecnt = 0;
    lclptr->ttis[0].tt_isdst = 0;
    lclptr->ttis[0].tt_gmtoff = 0;
    lclptr->ttis[0].tt_abbrind = 0;
    (void) strcpy(lclptr->chars, gmt);
  } else if (tzload(name, lclptr, TRUE) != 0)
    if (name[0] == ':' || tzparse(name, lclptr, FALSE) != 0) {
      (void) gmtload(lclptr);
    }
  settzname();
}

/*
** The easy way to behave "as if no library function calls" localtime
** is to not call it--so we drop its guts into "localsub", which can be
** freely called. (And no, the PANS doesn't require the above behavior--
** but it *is* desirable.)
**
** The unused offset argument is for the benefit of mktime variants.
*/

/*ARGSUSED*/
static struct tm *
localsub(const time_t *const timep, const int_fast32_t offset,
         struct tm *const tmp)
{
  register struct state    *sp;
  register const struct ttinfo   *ttisp;
  register int      i;
  register struct tm     *result;
  const time_t      t = *timep;

  sp = lclptr;
#ifdef ALL_STATE
  if (sp == NULL) {
    return gmtsub(timep, offset, tmp);
  }
#endif /* defined ALL_STATE */
  if ((sp->goback && t < sp->ats[0]) ||
      (sp->goahead && t > sp->ats[sp->timecnt - 1])) {
    time_t      newt = t;
    register time_t   seconds;
    register time_t   years;

    if (t < sp->ats[0]) {
      seconds = sp->ats[0] - t;
    } else { seconds = t - sp->ats[sp->timecnt - 1]; }
    --seconds;
    years = (seconds / SECSPERREPEAT + 1) * YEARSPERREPEAT;
    seconds = years * AVGSECSPERYEAR;
    if (t < sp->ats[0]) {
      newt += seconds;
    } else { newt -= seconds; }
    if (newt < sp->ats[0] ||
        newt > sp->ats[sp->timecnt - 1]) {
      return NULL;  /* "cannot happen" */
    }
    result = localsub(&newt, offset, tmp);
    if (result == tmp) {
      register time_t newy;

      newy = tmp->tm_year;
      if (t < sp->ats[0]) {
        newy -= years;
      } else { newy += years; }
      tmp->tm_year = newy;
      if (tmp->tm_year != newy) {
        return NULL;
      }
    }
    return result;
  }
  if (sp->timecnt == 0 || t < sp->ats[0]) {
    i = sp->defaulttype;
  } else {
    register int  lo = 1;
    register int  hi = sp->timecnt;

    while (lo < hi) {
      register int  mid = (lo + hi) >> 1;

      if (t < sp->ats[mid]) {
        hi = mid;
      } else { lo = mid + 1; }
    }
    i = (int) sp->types[lo - 1];
  }
  ttisp = &sp->ttis[i];
  /*
  ** To get (wrong) behavior that's compatible with System V Release 2.0
  ** you'd replace the statement below with
  **  t += ttisp->tt_gmtoff;
  **  timesub(&t, 0L, sp, tmp);
  */
  result = timesub(&t, ttisp->tt_gmtoff, sp, tmp);
  tmp->tm_isdst = ttisp->tt_isdst;
  tzname[tmp->tm_isdst] = &sp->chars[ttisp->tt_abbrind];
#ifdef TM_ZONE
  tmp->TM_ZONE = &sp->chars[ttisp->tt_abbrind];
#endif /* defined TM_ZONE */
  return result;
}

struct tm *
localtime(const time_t *const timep)
{
  tzset();
  return localsub(timep, 0L, &tm);
}

/*
** Re-entrant version of localtime.
*/

struct tm *
localtime_r(const time_t *const timep, struct tm *tmp)
{
  return localsub(timep, 0L, tmp);
}

/*
** gmtsub is to gmtime as localsub is to localtime.
*/

static struct tm *
gmtsub(const time_t *const timep, const int_fast32_t offset,
       struct tm *const tmp)
{
  register struct tm   *result;

  if (!gmt_is_set) {
    gmt_is_set = TRUE;
#ifdef ALL_STATE
    gmtptr = calloc(1, sizeof * gmtptr);
    if (gmtptr != NULL)
#endif /* defined ALL_STATE */
      gmtload(gmtptr);
  }
  result = timesub(timep, offset, gmtptr, tmp);
#ifdef TM_ZONE
  /*
  ** Could get fancy here and deliver something such as
  ** "UT+xxxx" or "UT-xxxx" if offset is non-zero,
  ** but this is no time for a treasure hunt.
  */
  if (offset != 0) {
    tmp->TM_ZONE = wildabbr;
  } else {
#ifdef ALL_STATE
    if (gmtptr == NULL) {
      tmp->TM_ZONE = gmt;
    } else { tmp->TM_ZONE = gmtptr->chars; }
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
    tmp->TM_ZONE = gmtptr->chars;
#endif /* State Farm */
  }
#endif /* defined TM_ZONE */
  return result;
}

struct tm *
gmtime(const time_t *const timep)
{
  return gmtsub(timep, 0L, &tm);
}

/*
* Re-entrant version of gmtime.
*/

struct tm *
gmtime_r(const time_t *const timep, struct tm *tmp)
{
  return gmtsub(timep, 0L, tmp);
}

#ifdef STD_INSPIRED

struct tm *
offtime(const time_t *const timep, const long offset)
{
  return gmtsub(timep, offset, &tm);
}

#endif /* defined STD_INSPIRED */

/*
** Return the number of leap years through the end of the given year
** where, to make the math easy, the answer for year zero is defined as zero.
*/

static int
leaps_thru_end_of(register const int y)
{
  return (y >= 0) ? (y / 4 - y / 100 + y / 400) :
         -(leaps_thru_end_of(-(y + 1)) + 1);
}

static struct tm *
timesub(const time_t *const timep, const int_fast32_t offset,
        register const struct state *const sp,
        register struct tm *const tmp)
{
  register const struct lsinfo   *lp;
  register time_t     tdays;
  register int      idays;  /* unsigned would be so 2003 */
  register int_fast64_t   rem;
  int       y;
  register const int     *ip;
  register int_fast64_t   corr;
  register int      hit;
  register int      i;

  corr = 0;
  hit = 0;
#ifdef ALL_STATE
  i = (sp == NULL) ? 0 : sp->leapcnt;
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
  i = sp->leapcnt;
#endif /* State Farm */
  while (--i >= 0) {
    lp = &sp->lsis[i];
    if (*timep >= lp->ls_trans) {
      if (*timep == lp->ls_trans) {
        hit = ((i == 0 && lp->ls_corr > 0) ||
               lp->ls_corr > sp->lsis[i - 1].ls_corr);
        if (hit)
          while (i > 0 &&
                 sp->lsis[i].ls_trans ==
                 sp->lsis[i - 1].ls_trans + 1 &&
                 sp->lsis[i].ls_corr ==
                 sp->lsis[i - 1].ls_corr + 1) {
            ++hit;
            --i;
          }
      }
      corr = lp->ls_corr;
      break;
    }
  }
  y = EPOCH_YEAR;
  tdays = *timep / SECSPERDAY;
  rem = *timep - tdays * SECSPERDAY;
  while (tdays < 0 || tdays >= year_lengths[isleap(y)]) {
    int   newy;
    register time_t tdelta;
    register int  idelta;
    register int  leapdays;

    tdelta = tdays / DAYSPERLYEAR;
    if (!((! TYPE_SIGNED(time_t) || INT_MIN <= tdelta)
          && tdelta <= INT_MAX)) {
      return NULL;
    }
    idelta = tdelta;
    if (idelta == 0) {
      idelta = (tdays < 0) ? -1 : 1;
    }
    newy = y;
    if (increment_overflow(&newy, idelta)) {
      return NULL;
    }
    leapdays = leaps_thru_end_of(newy - 1) -
               leaps_thru_end_of(y - 1);
    tdays -= ((time_t) newy - y) * DAYSPERNYEAR;
    tdays -= leapdays;
    y = newy;
  }
  {
    register int_fast32_t seconds;

    seconds = tdays * SECSPERDAY;
    tdays = seconds / SECSPERDAY;
    rem += seconds - tdays * SECSPERDAY;
  }
  /*
  ** Given the range, we can now fearlessly cast...
  */
  idays = tdays;
  rem += offset - corr;
  while (rem < 0) {
    rem += SECSPERDAY;
    --idays;
  }
  while (rem >= SECSPERDAY) {
    rem -= SECSPERDAY;
    ++idays;
  }
  while (idays < 0) {
    if (increment_overflow(&y, -1)) {
      return NULL;
    }
    idays += year_lengths[isleap(y)];
  }
  while (idays >= year_lengths[isleap(y)]) {
    idays -= year_lengths[isleap(y)];
    if (increment_overflow(&y, 1)) {
      return NULL;
    }
  }
  tmp->tm_year = y;
  if (increment_overflow(&tmp->tm_year, -TM_YEAR_BASE)) {
    return NULL;
  }
  tmp->tm_yday = idays;
  /*
  ** The "extra" mods below avoid overflow problems.
  */
  tmp->tm_wday = EPOCH_WDAY +
                 ((y - EPOCH_YEAR) % DAYSPERWEEK) *
                 (DAYSPERNYEAR % DAYSPERWEEK) +
                 leaps_thru_end_of(y - 1) -
                 leaps_thru_end_of(EPOCH_YEAR - 1) +
                 idays;
  tmp->tm_wday %= DAYSPERWEEK;
  if (tmp->tm_wday < 0) {
    tmp->tm_wday += DAYSPERWEEK;
  }
  tmp->tm_hour = (int)(rem / SECSPERHOUR);
  rem %= SECSPERHOUR;
  tmp->tm_min = (int)(rem / SECSPERMIN);
  /*
  ** A positive leap second requires a special
  ** representation. This uses "... ??:59:60" et seq.
  */
  tmp->tm_sec = (int)(rem % SECSPERMIN) + hit;
  ip = mon_lengths[isleap(y)];
  for (tmp->tm_mon = 0; idays >= ip[tmp->tm_mon]; ++(tmp->tm_mon)) {
    idays -= ip[tmp->tm_mon];
  }
  tmp->tm_mday = (int)(idays + 1);
  tmp->tm_isdst = 0;
#ifdef TM_GMTOFF
  tmp->TM_GMTOFF = offset;
#endif /* defined TM_GMTOFF */
  return tmp;
}

char *
ctime(const time_t *const timep)
{
  /*
  ** Section 4.12.3.2 of X3.159-1989 requires that
  **  The ctime function converts the calendar time pointed to by timer
  **  to local time in the form of a string. It is equivalent to
  **    asctime(localtime(timer))
  */
  return asctime(localtime(timep));
}

char *
ctime_r(const time_t *const timep, char *buf)
{
  struct tm mytm;

  return asctime_r(localtime_r(timep, &mytm), buf);
}

/*
** Adapted from code provided by Robert Elz, who writes:
**  The "best" way to do mktime I think is based on an idea of Bob
**  Kridle's (so its said...) from a long time ago.
**  It does a binary search of the time_t space. Since time_t's are
**  just 32 bits, its a max of 32 iterations (even at 64 bits it
**  would still be very reasonable).
*/

#ifndef WRONG
#define WRONG (-1)
#endif /* !defined WRONG */

/*
** Normalize logic courtesy Paul Eggert.
*/

static int
increment_overflow(int *const ip, int j)
{
  register int const  i = *ip;

  /*
  ** If i >= 0 there can only be overflow if i + j > INT_MAX
  ** or if j > INT_MAX - i; given i >= 0, INT_MAX - i cannot overflow.
  ** If i < 0 there can only be overflow if i + j < INT_MIN
  ** or if j < INT_MIN - i; given i < 0, INT_MIN - i cannot overflow.
  */
  if ((i >= 0) ? (j > INT_MAX - i) : (j < INT_MIN - i)) {
    return TRUE;
  }
  *ip += j;
  return FALSE;
}

static int
increment_overflow32(int_fast32_t *const lp, int const m)
{
  register int_fast32_t const l = *lp;

  if ((l >= 0) ? (m > INT_FAST32_MAX - l) : (m < INT_FAST32_MIN - l)) {
    return TRUE;
  }
  *lp += m;
  return FALSE;
}

static int
normalize_overflow(int *const tensptr, int *const unitsptr, const int base)
{
  register int  tensdelta;

  tensdelta = (*unitsptr >= 0) ?
              (*unitsptr / base) :
              (-1 - (-1 - *unitsptr) / base);
  *unitsptr -= tensdelta * base;
  return increment_overflow(tensptr, tensdelta);
}

static int
normalize_overflow32(int_fast32_t *const tensptr, int *const unitsptr,
                     const int base)
{
  register int  tensdelta;

  tensdelta = (*unitsptr >= 0) ?
              (*unitsptr / base) :
              (-1 - (-1 - *unitsptr) / base);
  *unitsptr -= tensdelta * base;
  return increment_overflow32(tensptr, tensdelta);
}

static int
tmcomp(register const struct tm *const atmp,
       register const struct tm *const btmp)
{
  register int  result;

  if (atmp->tm_year != btmp->tm_year) {
    return atmp->tm_year < btmp->tm_year ? -1 : 1;
  }
  if ((result = (atmp->tm_mon - btmp->tm_mon)) == 0 &&
      (result = (atmp->tm_mday - btmp->tm_mday)) == 0 &&
      (result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
      (result = (atmp->tm_min - btmp->tm_min)) == 0) {
    result = atmp->tm_sec - btmp->tm_sec;
  }
  return result;
}

static time_t
time2sub(struct tm *const tmp,
         struct tm * (*const funcp)(const time_t *, int_fast32_t, struct tm *),
         const int_fast32_t offset,
         int *const okayp,
         const int do_norm_secs)
{
  register const struct state  *sp;
  register int      dir;
  register int      i, j;
  register int      saved_seconds;
  register int_fast32_t     li;
  register time_t     lo;
  register time_t     hi;
  int_fast32_t        y;
  time_t        newt;
  time_t        t;
  struct tm     yourtm, mytm;

  *okayp = FALSE;
  yourtm = *tmp;
  if (do_norm_secs) {
    if (normalize_overflow(&yourtm.tm_min, &yourtm.tm_sec,
                           SECSPERMIN)) {
      return WRONG;
    }
  }
  if (normalize_overflow(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR)) {
    return WRONG;
  }
  if (normalize_overflow(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY)) {
    return WRONG;
  }
  y = yourtm.tm_year;
  if (normalize_overflow32(&y, &yourtm.tm_mon, MONSPERYEAR)) {
    return WRONG;
  }
  /*
  ** Turn y into an actual year number for now.
  ** It is converted back to an offset from TM_YEAR_BASE later.
  */
  if (increment_overflow32(&y, TM_YEAR_BASE)) {
    return WRONG;
  }
  while (yourtm.tm_mday <= 0) {
    if (increment_overflow32(&y, -1)) {
      return WRONG;
    }
    li = y + (1 < yourtm.tm_mon);
    yourtm.tm_mday += year_lengths[isleap(li)];
  }
  while (yourtm.tm_mday > DAYSPERLYEAR) {
    li = y + (1 < yourtm.tm_mon);
    yourtm.tm_mday -= year_lengths[isleap(li)];
    if (increment_overflow32(&y, 1)) {
      return WRONG;
    }
  }
  for (; ;) {
    i = mon_lengths[isleap(y)][yourtm.tm_mon];
    if (yourtm.tm_mday <= i) {
      break;
    }
    yourtm.tm_mday -= i;
    if (++yourtm.tm_mon >= MONSPERYEAR) {
      yourtm.tm_mon = 0;
      if (increment_overflow32(&y, 1)) {
        return WRONG;
      }
    }
  }
  if (increment_overflow32(&y, -TM_YEAR_BASE)) {
    return WRONG;
  }
  yourtm.tm_year = y;
  if (yourtm.tm_year != y) {
    return WRONG;
  }
  if (yourtm.tm_sec >= 0 && yourtm.tm_sec < SECSPERMIN) {
    saved_seconds = 0;
  } else if (y + TM_YEAR_BASE < EPOCH_YEAR) {
    /*
    ** We can't set tm_sec to 0, because that might push the
    ** time below the minimum representable time.
    ** Set tm_sec to 59 instead.
    ** This assumes that the minimum representable time is
    ** not in the same minute that a leap second was deleted from,
    ** which is a safer assumption than using 58 would be.
    */
    if (increment_overflow(&yourtm.tm_sec, 1 - SECSPERMIN)) {
      return WRONG;
    }
    saved_seconds = yourtm.tm_sec;
    yourtm.tm_sec = SECSPERMIN - 1;
  } else {
    saved_seconds = yourtm.tm_sec;
    yourtm.tm_sec = 0;
  }
  /*
  ** Do a binary search (this works whatever time_t's type is).
  */
  if (!TYPE_SIGNED(time_t)) {
    lo = 0;
    hi = lo - 1;
  } else {
    lo = 1;
    for (i = 0; i < (int) TYPE_BIT(time_t) - 1; ++i) {
      lo *= 2;
    }
    hi = -(lo + 1);
  }
  for (; ;) {
    t = lo / 2 + hi / 2;
    if (t < lo) {
      t = lo;
    } else if (t > hi) {
      t = hi;
    }
    if ((*funcp)(&t, offset, &mytm) == NULL) {
      /*
      ** Assume that t is too extreme to be represented in
      ** a struct tm; arrange things so that it is less
      ** extreme on the next pass.
      */
      dir = (t > 0) ? 1 : -1;
    } else { dir = tmcomp(&mytm, &yourtm); }
    if (dir != 0) {
      if (t == lo) {
        if (t == time_t_max) {
          return WRONG;
        }
        ++t;
        ++lo;
      } else if (t == hi) {
        if (t == time_t_min) {
          return WRONG;
        }
        --t;
        --hi;
      }
      if (lo > hi) {
        return WRONG;
      }
      if (dir > 0) {
        hi = t;
      } else { lo = t; }
      continue;
    }
    if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst) {
      break;
    }
    /*
    ** Right time, wrong type.
    ** Hunt for right time, right type.
    ** It's okay to guess wrong since the guess
    ** gets checked.
    */
    sp = (const struct state *)
         ((funcp == localsub) ? lclptr : gmtptr);
#ifdef ALL_STATE
    if (sp == NULL) {
      return WRONG;
    }
#endif /* defined ALL_STATE */
    for (i = sp->typecnt - 1; i >= 0; --i) {
      if (sp->ttis[i].tt_isdst != yourtm.tm_isdst) {
        continue;
      }
      for (j = sp->typecnt - 1; j >= 0; --j) {
        if (sp->ttis[j].tt_isdst == yourtm.tm_isdst) {
          continue;
        }
        newt = t + sp->ttis[j].tt_gmtoff -
               sp->ttis[i].tt_gmtoff;
        if ((*funcp)(&newt, offset, &mytm) == NULL) {
          continue;
        }
        if (tmcomp(&mytm, &yourtm) != 0) {
          continue;
        }
        if (mytm.tm_isdst != yourtm.tm_isdst) {
          continue;
        }
        /*
        ** We have a match.
        */
        t = newt;
        goto label;
      }
    }
    return WRONG;
  }
label:
  newt = t + saved_seconds;
  if ((newt < t) != (saved_seconds < 0)) {
    return WRONG;
  }
  t = newt;
  if ((*funcp)(&t, offset, tmp)) {
    *okayp = TRUE;
  }
  return t;
}

static time_t
time2(struct tm *const tmp,
      struct tm * (*const funcp)(const time_t *, int_fast32_t, struct tm *),
      const int_fast32_t offset,
      int *const okayp)
{
  time_t  t;

  /*
  ** First try without normalization of seconds
  ** (in case tm_sec contains a value associated with a leap second).
  ** If that fails, try with normalization of seconds.
  */
  t = time2sub(tmp, funcp, offset, okayp, FALSE);
  return *okayp ? t : time2sub(tmp, funcp, offset, okayp, TRUE);
}

static time_t
time1(struct tm *const tmp,
      struct tm * (*const funcp)(const time_t *, int_fast32_t, struct tm *),
      const int_fast32_t offset)
{
  register time_t     t;
  register const struct state  *sp;
  register int      samei, otheri;
  register int      sameind, otherind;
  register int      i;
  register int      nseen;
  int       seen[TZ_MAX_TYPES];
  int       types[TZ_MAX_TYPES];
  int       okay;

  if (tmp == NULL) {
    errno = EINVAL;
    return WRONG;
  }
  if (tmp->tm_isdst > 1) {
    tmp->tm_isdst = 1;
  }
  t = time2(tmp, funcp, offset, &okay);
#ifdef PCTS
  /*
  ** PCTS code courtesy Grant Sullivan.
  */
  if (okay) {
    return t;
  }
  if (tmp->tm_isdst < 0) {
    tmp->tm_isdst = 0;  /* reset to std and try again */
  }
#endif /* defined PCTS */
#ifndef PCTS
  if (okay || tmp->tm_isdst < 0) {
    return t;
  }
#endif /* !defined PCTS */
  /*
  ** We're supposed to assume that somebody took a time of one type
  ** and did some math on it that yielded a "struct tm" that's bad.
  ** We try to divine the type they started from and adjust to the
  ** type they need.
  */
  sp = (const struct state *)((funcp == localsub) ?  lclptr : gmtptr);
#ifdef ALL_STATE
  if (sp == NULL) {
    return WRONG;
  }
#endif /* defined ALL_STATE */
  for (i = 0; i < sp->typecnt; ++i) {
    seen[i] = FALSE;
  }
  nseen = 0;
  for (i = sp->timecnt - 1; i >= 0; --i)
    if (!seen[sp->types[i]]) {
      seen[sp->types[i]] = TRUE;
      types[nseen++] = sp->types[i];
    }
  for (sameind = 0; sameind < nseen; ++sameind) {
    samei = types[sameind];
    if (sp->ttis[samei].tt_isdst != tmp->tm_isdst) {
      continue;
    }
    for (otherind = 0; otherind < nseen; ++otherind) {
      otheri = types[otherind];
      if (sp->ttis[otheri].tt_isdst == tmp->tm_isdst) {
        continue;
      }
      tmp->tm_sec += sp->ttis[otheri].tt_gmtoff -
                     sp->ttis[samei].tt_gmtoff;
      tmp->tm_isdst = !tmp->tm_isdst;
      t = time2(tmp, funcp, offset, &okay);
      if (okay) {
        return t;
      }
      tmp->tm_sec -= sp->ttis[otheri].tt_gmtoff -
                     sp->ttis[samei].tt_gmtoff;
      tmp->tm_isdst = !tmp->tm_isdst;
    }
  }
  return WRONG;
}

time_t
mktime(struct tm *const tmp)
{
  return time1(tmp, localsub, 0L);
}

#ifdef STD_INSPIRED

time_t
timelocal(struct tm *const tmp)
{
  if (tmp != NULL) {
    tmp->tm_isdst = -1;  /* in case it wasn't initialized */
  }
  return mktime(tmp);
}

time_t
timegm(struct tm *const tmp)
{
  if (tmp != NULL) {
    tmp->tm_isdst = 0;
  }
  return time1(tmp, gmtsub, 0L);
}

time_t
timeoff(struct tm *const tmp, const long offset)
{
  if (tmp != NULL) {
    tmp->tm_isdst = 0;
  }
  return time1(tmp, gmtsub, offset);
}

#endif /* defined STD_INSPIRED */

#ifdef CMUCS

/*
** The following is supplied for compatibility with
** previous versions of the CMUCS runtime library.
*/

long
gtime(struct tm *const tmp)
{
  const time_t  t = mktime(tmp);

  if (t == WRONG) {
    return -1;
  }
  return t;
}

#endif /* defined CMUCS */

/*
** XXX--is the below the right way to conditionalize??
*/

#ifdef STD_INSPIRED

/*
** IEEE Std 1003.1-1988 (POSIX) legislates that 536457599
** shall correspond to "Wed Dec 31 23:59:59 UTC 1986", which
** is not the case if we are accounting for leap seconds.
** So, we provide the following conversion routines for use
** when exchanging timestamps with POSIX conforming systems.
*/

static int_fast64_t
leapcorr(time_t *timep)
{
  register struct state    *sp;
  register struct lsinfo   *lp;
  register int      i;

  sp = lclptr;
  i = sp->leapcnt;
  while (--i >= 0) {
    lp = &sp->lsis[i];
    if (*timep >= lp->ls_trans) {
      return lp->ls_corr;
    }
  }
  return 0;
}

time_t
time2posix(time_t t)
{
  tzset();
  return t - leapcorr(&t);
}

time_t
posix2time(time_t t)
{
  time_t  x;
  time_t  y;

  tzset();
  /*
  ** For a positive leap second hit, the result
  ** is not unique. For a negative leap second
  ** hit, the corresponding time doesn't exist,
  ** so we return an adjacent second.
  */
  x = t + leapcorr(&t);
  y = x - leapcorr(&x);
  if (y < t) {
    do {
      x++;
      y = x - leapcorr(&x);
    } while (y < t);
    if (t != y) {
      return x - 1;
    }
  } else if (y > t) {
    do {
      --x;
      y = x - leapcorr(&x);
    } while (y > t);
    if (t != y) {
      return x + 1;
    }
  }
  return x;
}

#endif /* defined STD_INSPIRED */
